JPS6141992A - Preventive system of evaporation of pool water in nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device for preventing a large amount of pool water from evaporating in large quantities, and is particularly used in a nuclear reactor pool such as a spent fuel storage pool. This invention relates to a nuclear reactor pool water evaporation prevention system suitable for.

[Background of the invention]

In indoor pools such as spent fuel storage pools installed at nuclear power plants, water is stored for the purpose of removing heat from the spent fuel and shielding it from radiation, but the pool water temperature limit reaches approximately 65°C. I'm here.

Since the temperature is higher than the temperature inside the pool, the amount of evaporation of the pool water is extremely large. Therefore, in order to replenish pool water lost due to evaporation, a system such as a fuel pool makeup water system (hereinafter abbreviated as FPMVv) is operated to supply a large amount of water.

Also, for the same reason, that is, the pool water temperature is higher than the air temperature inside the pool.

Water vapor from the pool water rises and diffuses, resulting in high temperature and high humidity inside the pool, creating a harsh working environment for workers during periodic inspections of nuclear reactors.

Also, condensation forms on the walls and ceiling of the pool room.
The condensation may fall as water droplets and contaminate the workers' clothing.

Furthermore, dust gets mixed into the pool water, becomes radioactive due to spent fuel, etc., and diffuses into the pool room along with water vapor when the pool water evaporates, increasing the atmospheric radiation dose inside the pool room and causing workers to This has a large effect on the exposure dose.

As mentioned above, although the indoor pool room such as the spent fuel storage pool installed at the 1M nuclear power plant provides a harsh working environment for the five workers, the The amount of work involved is quite large, and this poses a major problem from the standpoint of worker safety and health.

From the above background, it is necessary to install a pool water evaporation prevention device or ventilation air conditioning equipment.

Conventionally, this method of ventilation and air conditioning in the pool room was carried out using a duct branched from the supply air duct and exhaust duct of the reactor building ventilation and air conditioning system. Air was exhausted from the room and through exhaust ducts installed above the water surface of the pool, providing basic ventilation within the room. However, in this method, since the exhaust duct opening is formed in the pool wall, the suction effect is small in the central area of the pool water surface, and the amount of water vapor evaporated increases accordingly.

The phenomenon described above is unavoidable.

The device described in JP-A No. 55-48698 installs a dedicated cooling device (air conditioner) inside the pool room to (1) maintain a comfortable working environment temperature for workers;
This device is characterized by providing temperature conditions (2) preventing condensation from forming on wall surfaces in the pool room, and (3) reducing radiation exposure to workers and the reactor pool. does not prevent evaporation and diffusion from the pool water surface, which is the root cause of the above problem, so it is necessary to (1) prevent evaporation of pool water, (2) suppress atmospheric radiation dose, and (3) prevent dust from entering pool water. No consideration was given to preventing the contamination of other substances.

Additionally, the device described in Utility Model Application No. 55-109900 lowers the radiation level on the first working floor by covering the entire upper surface of the pool with a sheet-like cover, making it possible to minimize the amount of evaporated water caused by air conditioning. It is something. However, in order to undergo daily inspection work, it is necessary to ensure visibility of the internal condition of the pool, but this device must be opened and closed for inspection. For this reason, it is possible to use glass or a transparent vinyl sheet for the cover, but since radiation is emitted from the pool, glass or vinyl sheets may cause so-called devitrification, or the internal The water vapor generated during this process causes water droplets to adhere to the inner surface of the cover, making it extremely difficult to ensure visibility into the interior. In addition, this device must be left open and the inside of the pool must be accessed during regular inspections, and when the device is opened, a large amount of water vapor leaks into the pool room. It's a long way off. Also, dust.

No consideration was given to the fact that the upper part of the pool cannot be covered during regular inspections, which often occur.

[Purpose of the invention]

The purpose of the present invention is to solve the problems of such conventional methods and (
1) Preventing the evaporation of pool water (2) Suppressing the dose in the indoor pool atmosphere (3) Preventing dust from entering the pool water (4) Ensuring visibility of the situation inside the pool (5) Ease of access to the pool (workability) ) and (6) prolonging the make-up water supply cycle to the pool.

[Summary of the invention]

The present invention has the following advantages: (1) By forcibly supplying and exhausting air from an air outlet and an air intake directly above the surface of the pool water,
Forming an air curtain on the surface of the pool water and (
2) The purpose is to be achieved by forcibly taking in water vapor from the pool water surface through the suction port, converting this water vapor into water using the connected steam condensation amount, and then resupplying this water to the pool. It is something to do.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a conceptual diagram of a system in which the present invention is applied to a nuclear reactor pool such as a spent fuel pool.

In FIG. 1, 1 indicates a pool, and 2 indicates boule water. Among the walls of the pool, one set of opposing walls has an opening parallel to the water surface, just above the water surface. There is. One of these openings is an outlet 3 for the air forming the air curtain, and the other is an inlet 4.

FIG. 2 is a representation of cross section AA in FIG. 1.

Air discharge port 3. Ventilation fi5 is installed so that an air curtain can be formed on the pool water surface using the air suction port 4.
．． and a ventilation fan 6. A ventilation fan 5 is installed to send out air above the pool water surface, and a ventilation fan 6 is installed to suck in the sent out air.

Ventilation fan5. As the equipment used as the ventilation fan 6, it is possible to use equipment that is widely sold and used as a ventilation fan for air curtains.

According to Japanese Patent Application Laid-Open No. 55-48698, water vapor rises and diffuses from the pool water surface, but in order to provide ventilation air conditioning (so-called air curtain) to prevent this rise of water vapor, the surface area of the pool increases. It is said that it has not been adopted because it is large and difficult due to restrictions on the size of the exhaust duct installed directly above the pool water surface. However, air curtains that are widely sold and used on the pool water surface are not effective enough to meet the purpose of this system due to specifications such as discharge/intake air volume and the shape of ventilation fans. It is currently possible to obtain this by using a ventilation door.

First, regarding the issue of exhaust duct size.

Discharge port 3. This can be solved by arranging several suction ports 4 in the longitudinal direction. The size of the opening (pool water surface) of a typical nuclear reactor pool is approximately 13 m in the vertical direction and approximately 12 m in the horizontal direction. Among the air curtain ventilation fans widely sold and used in general, the largest one is capable of discharging and inhaling air over a width of approximately 2 meters, so it can be handled by arranging several of these. .

Additionally, since the surface area of the pool is extremely large, it is not possible to obtain the air curtain effect required by a single system, so currently, a large air volume type air curtain ventilation fan is used.

It is manageable. This has been proven by the fact that special air curtain ventilation fans are installed at high entrances to factories and electrical buildings. Or, even if it is not widely sold or used, the air volume of the ventilation fan for the air curtain.

This can be easily dealt with by making it larger.

Also, by using a separate ventilation fan on the suction side as shown in FIG. 1, the formation of the air curtain becomes more effective and better.

By configuring and installing the device as described above, it is possible to form an air curtain directly above the pool water surface, which is the first function of this system.

The water vapor evaporated from the pool water surface by the air flow of the air curtain described above does not diffuse to the upper part of the air curtain, but is sucked into the suction port 4.

Air containing water vapor is passed through a duct 7 to a water condensing device 8
The device converts the water vapor back into water. In addition, the air curtain suppresses the diffusion of radioactive substances mixed with water vapor and evaporated from above the water surface, and is guided through the duct 7 to the water condensing device 8 and returned to the water. The water thus returned from the steam is re-supplied to the pool 1 from the water supply port 11 through the pipe 10 connected to the pool 1 by the pump 9. In addition, as shown in Figure 3, water condensing system [8 and pool 1]
If a salt filtration device 12 is provided between them, it is effective to reduce contamination of the pool water 2.

What has been explained above is an example of this system, and modifications can be made without changing the intention of this system.For example, if the equipment that makes up the air curtain is made mobile, It is also possible to move and use the surface.

In addition, by controlling the air volume of the air curtain, a strong air curtain is formed when there is a large amount of work inside the pool, such as during regular inspections, which improves the working environment for each worker, and normally does not interfere with regular inspections. It is also possible to create an air curtain that does not cause any damage.

〔Effect of the invention〕

According to this system, by forming an air curtain,
Since the diffusion of water vapor and radioactive substances to the upper part of the air curtain is suppressed, it is possible to maintain a good working environment in the pool room and to suppress the atmospheric radiation dose to a low level. Furthermore, the air curtain prevents dust from entering the pool from entering the pool, which is also effective in preventing radioactive contamination.

In addition, by using an air curtain, visibility to the inside of the pool can be ensured, making it unnecessary to remove the cover when using a cover.Furthermore, while preventing the diffusion of water vapor, it is possible to ensure visibility into the inside of the pool. This has the effect of free access.

Furthermore, a water condensing device returns the evaporated water to its original state, preventing the spread of radiation contamination.
This has the effect of shortening the interval between replenishment water using the MUV system.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram showing an example of this system, and Figure 2 is a conceptual diagram showing an example of this system.
3 is a conceptual diagram showing an example of expansion of this system. 1... Reactor pool, 2... Reactor pool water, 3.
...Discharge port, 4...Intake port, 5...Ventilation fan (for discharge), 6...Ventilation fan (for suction), 7...Duct, 8...
・Water condensing device, 9...Pump, 10...Piping, 11
... Water supply port, 12 ... Salt filtration device, 13 ... Water vapor, 14 ... Air curtain.

Claims (1)

[Claims] 1. In a nuclear reactor such as a spent fuel storage pool in a reactor building in a nuclear power plant, an air outlet 12 and an air inlet are installed above the water surface of the pool, and a compressor or fan is used to remove air. A steam condensing device that forms an air curtain at the pool opening by forcibly supplying and exhausting water, converts the water vapor contained in the air collected from the air intake port of the air curtain into water, and returns it to the pool. A nuclear reactor pool water evaporation prevention system characterized by having.